In production or manufacturing industries, integration of automatic flow lines or automation to the processes involved in production manufacturing is gaining importance due to improved product quality, high repeatability, high positioning accuracy and operating time reduction. Automation also greatly decreases the need for continuous human intervention while increasing load capacity, speed and safety. Machine safety logic, governs the automation to perform specific operations including clamping and unclamping of the work pieces.
One way of clamping and unclamping the work pieces, is carried out using clamping devices such as link clamp cylinders because the link clamp cylinders takes minimum space requirements as there is no swiveling motion of the clamp lever during clamping and unclamping operations. These link clamp cylinders are operated by displacement of hydraulically or pneumatically actuated piston appropriately linked to the link clamp assembly to facilitate clamping and unclamping operations. The link clamp cylinders are placed in required position in an automation system which can hold work pieces, so that the other components of the automation can carry out their pre-set functions on the work piece. After completion of operations, the work piece is unclamped by the link clamp cylinder. Thus, unclamp sensing becomes important in automation because if the work piece is not properly unclamped, the automation system will move the work piece, which is neither clamped nor unclamped rigidly and may cause serious accident in the shop floor and the operators. Hence automation system without feedback unit has disadvantages, predominant one being vulnerability, which makes the automation more prone to errors or mistakes which will have serious consequences or accidents while operating.
For example, in a gantry system used to pick and place heavy work pieces in a shop floor of an industry. The gantry consists of fixture appropriately mounted on a guide way, to hold the work piece that is to be picked and placed, and machine safety logic to govern the movement of the fixture. The machine safety logic first sends signals appropriately so that the fixture clamps the work piece. After clamping the work piece, the work piece is then transferred to a predetermined location at a predetermined speed. A controller in the gantry system sends signals appropriately to machine safety logic, so that the fixture unclamps the work piece. If the unclamping is not carried out properly, the gantry moves the work piece and may cause serious accident in the work space. Hence, safety in automation system becomes a predominant aspect to be considered while constructing any automation system and hence there exist a need of a mechanism for unclamp sensing in the link clamp cylinders used in automation. The safety in automation refers to safety of operators, fixtures and robot/gantry loader.
Further, in the existing link clamp cylinder the unclamp feedback unit is generally provided from the bottom of the link clamp cylinder. In base types of fixture applications use of this bottom pneumatic feedback unit is not feasible because of height and weight constraints. Unclamp sensing feedback unit at the bottom of the link clamp cylinder will increase the height of the cylinder, this increase in height will obstruct the movement of cutting tools during operation. To compensate for the increase in height of link clamp cylinder, the cutting tool length has to be increased which is not desirable. Also, installing the unclamp feedback unit at the bottom of the link clamp cylinder will be expensive. And because of the additional feedback unit, weight of the whole component will increase which is not desirable.
In light of the foregoing discussion, it is necessary to develop unclamp sensing feedback unit which is economical and at the same time overcome the limitations stated above.